Thank you for your  reply.

Dual mine that you are talking about mining is the Claymore that they are talking about in this post https://bitcointalk.org/index.php?topic=1433925.0

About the power supply I'm pretty sure that can handle at least for start 2 GPU's, I will check my PSU to be sure if can handle even more GPU's

The RX 470 I can get for around $250 ~ $290, I will buy one and see, it's a little bit expensive here, but I think that it will be profitable anyway

And about the case, I will build one my own.

Your suggestion will be very helpful.

And i'm sorry to ask but do you have any suggestions where to start ? Mining software ? suggestion of pool ?